The reparation, adornment, and prosthetic extension of keratinaceous structures, namely, human fingernails and toe nails and livestock hoofs, has been a common practice for centuries. Fingernails are currently known to be coated with multicolored nitrocellulose lacquers, repaired with cyanoacrylate adhesives, and extended with the use of acrylic monomer and polymer slurries or doughs that cure by peroxide/amine free radical mechanisms. Although the nitrocellulose lacquers and the cyanoacylate adhesives are relatively adherent to a fingernail plate, the acrylic materials employed for the purpose of creating an artificial fingernail prosthesis are not. Only after treatment of the fingernail surface with an unsaturated carboxylic acid, such as methacrylic acid (current commercial embodiments contain in excess of 70 percent methacrylic acid), will such acrylic monomer and polymer slurries or doughs adhere to the nail plate. Such harsh treatment on a relatively fragile surface poses a serious toxicological hazard due to the corrosive nature of these unsaturated carboxylic acids. Other unsaturated carboxylic acids presently being used in the described applications include either alone or in part, acrylic acid and beta-carboxyethyl acrylate. Lower concentrations of these unsaturated acids pose a decreased danger to the intact fingernail surface; however, at such lower concentrations the adhesion of the acrylic monomer and polymer slurry is minimized or lost completely. An analagous situation exists when attempting to repair a split or fractured hoof in that without the application of the corrosive and possibly toxic levels of unsaturated acids, very poor adhesion results.
Currently, the only known and readily practiced method for obtaining adhesion of prosthetic materials to wholly proteinaceous substrates, such as fingernails and hooves, has been the physical abrasion and roughening of the proteinaceous substrate surface with a file, sandpaper-like, or other abrasive material, followed by the application of unsaturated carboxylic acid solutions (in the artificial fingernail art known as primers), followed lastly by the application of the prosthetic material. The prosthetic material is not inherently to proteinaceous substrates. Rather, the prosthetic material also contains unsaturated groups, which, when cured, chemically bind with the unsaturated groups of the carboxylic acid solution applied to the proteinaceous substrate. Thus, an adhesive bond between said substrate and the prosthesis is provided.
The disadvantages of such a method and materials used in the prior art are as follows:
(1) too much physical abrasion or roughening of the proteinaceous substrate, particularly a living fingernail, can be harmful to the individual;
(2) in the area of hoof binding, cracks and fissures in the hooves are not readily abraded or roughened due to the inaccessability of the surface to such abrasive materials and methods;
(3) the unsaturated carboxylic acids that are often used (acrylic acid and methacrylic acid, either alone at full concentration or in combination with other diluents, are highly corrosive and can severely damage the protein of a fingernail or hoof or the underlying or surrounding living tissue; and
(4) even with such harsh surface preparation as described above, the adhesive bonds obtained with such methods are poor and all too often inadequate to retain the prosthetic for sufficient periods of time or under stress, thus causing the prosthetic to break off in whole or in part.